Many WMS clients, including the Godiva2 client (Blower et al., 2009a) that is bundled with ncWMS, are tiling clients that make GetMap requests using a finite number of fixed bounding boxes.
This increases the scalability of the system as a whole by permitting repeated requests for the same image to be served from application-level caches. ncWMS therefore implements such a cache (see architecture diagram in Fig. 2).
Note that this cache holds data arrays, not final images: this allows the user to change the styling parameters of an image (e.g. the colour palette) without re-extracting the data from the source files, speeding up interactive visualization. Many system administrators choose also to implement a tile cache on top of ncWMS, which can further increase performance and scalability.